Sample preparation devices for the extraction of nucleic acids from biological samples in accordance with the Boom method, or variations thereof, are known.
In the Boom method, nucleic acids (DNA and RNA) are extracted from biological samples by the binding of the nucleic acids to silica beads in the presence of chaotropic agents. The biological samples may be whole blood, blood serum, buffy coat (a density gradient centrifuged fraction of an anticoagulated blood sample containing white blood cells and platelets), urine, feces, cerebrospinal fluid, sperm, saliva, body tissues, nasal swabs, buccal swabs, cell cultures, food products, environmental water, soil, and vaccines, for example.
The chaotropic agents disrupt and denature the structure of the nucleic acids by interfering with the macromolecular interactions mediated by non-covalent forces, such as hydrogen bonding, van der Waals forces, and hydrophobic interactions, for example. In the presence of the chaotropic agents, water is removed from the phosphate groups of the nucleic acids, exposing them and allowing hydrophobic bonding to the silica. Protein, cellular debris, and other substances in the biological samples do not bond to the silica and are retained in the solution. Magnetic beads coated with silica may be used to assist in the separation of the nucleic acids bound to the silica coating from the solution.
In accordance with the Boom method, a biological sample is lysed and/or homogenized by mixing the biological sample with detergent in the presence of protein degrading enzymes. The chaotropic agents and silica or silica coated beads are mixed with the lysed biological sample, allowing nucleic acids to bond to the silica or silica coated beads. The silica beads are washed several times to remove non-nucleic acid materials, such as proteins, lipids, cellular constituents, including cellular molecules, and other substances found in biological samples. The nucleic acids are then eluted into a buffer from the silica or silica coated beads by decreasing the concentration of the chaotropic agents. The elution buffer may be pure water or Tris EDTA (“TE”) buffer for example.
U.S. Patent Publication No. 2009/0111193 A1 describes a sample preparation device including a housing defining a passage and a filter of monolith absorbent that binds nucleic acids passing through the filter. The monolith absorbent may be a glass frit, a porous glass monolith, or porous monolithic polymers. The glass frit may be sintered glass of crushed beads. Pore sizes may vary from about 2 microns to about 220 microns. One end of the housing has a pipette tip. Samples are drawn into the housing through the pipette tip by an electronic pipetter device such as an electronic pipetter or robotic pipetting station. The electronic pipetter draws the sample through the filter. The nucleic acids bonded to the filter are washed with ethanol and eluted by an elution buffer. The eluted nucleic acids are quantified by polymerase chain reaction (“PCR”).
The use of pipettes and electronic pipette devices is expensive. In addition, because of the large pore size, capture efficiency in U.S. Patent Application No. 2009/0111193A1 may be low and draw and discharge may be slow.